Actual source code: sro.c
1: #define PETSCMAT_DLL
3: #include ../src/mat/impls/baij/seq/baij.h
4: #include ../src/inline/spops.h
5: #include ../src/mat/impls/sbaij/seq/sbaij.h
6: #include petscsys.h
8: /*
9: This function is used before applying a
10: symmetric reordering to matrix A that is
11: in SBAIJ format.
13: The permutation is assumed to be symmetric, i.e.,
14: P = P^T (= inv(P)),
15: so the permuted matrix P*A*inv(P)=P*A*P^T is ensured to be symmetric.
16: - a wrong assumption! This code needs rework! -- Hong
18: The function is modified from sro.f of YSMP. The description from YSMP:
19: C THE NONZERO ENTRIES OF THE MATRIX M ARE ASSUMED TO BE STORED
20: C SYMMETRICALLY IN (IA,JA,A) FORMAT (I.E., NOT BOTH M(I,J) AND M(J,I)
21: C ARE STORED IF I NE J).
22: C
23: C SRO DOES NOT REARRANGE THE ORDER OF THE ROWS, BUT DOES MOVE
24: C NONZEROES FROM ONE ROW TO ANOTHER TO ENSURE THAT IF M(I,J) WILL BE
25: C IN THE UPPER TRIANGLE OF M WITH RESPECT TO THE NEW ORDERING, THEN
26: C M(I,J) IS STORED IN ROW I (AND THUS M(J,I) IS NOT STORED); WHEREAS
27: C IF M(I,J) WILL BE IN THE STRICT LOWER TRIANGLE OF M, THEN M(J,I) IS
28: C STORED IN ROW J (AND THUS M(I,J) IS NOT STORED).
31: -- output: new index set (inew, jnew) for A and a map a2anew that maps
32: values a to anew, such that all
33: nonzero A_(perm(i),iperm(k)) will be stored in the upper triangle.
34: Note: matrix A is not permuted by this function!
35: */
38: PetscErrorCode MatReorderingSeqSBAIJ(Mat A,IS perm)
39: {
40: Mat_SeqSBAIJ *a=(Mat_SeqSBAIJ *)A->data;
42: const PetscInt mbs=a->mbs,*rip,*riip;
43: PetscInt *ai,*aj,*r;
44: PetscInt *nzr,nz,jmin,jmax,j,k,ajk,i;
45: IS iperm; /* inverse of perm */
48: if (!mbs) return(0);
49: SETERRQ(PETSC_ERR_SUP,"Matrix reordering is not supported for sbaij matrix. Use aij format");
50: ISGetIndices(perm,&rip);
52: ISInvertPermutation(perm,PETSC_DECIDE,&iperm);
53: ISGetIndices(iperm,&riip);
55: for (i=0; i<mbs; i++) {
56: if (rip[i] != riip[i]) SETERRQ(PETSC_ERR_ARG_INCOMP,"Non-symmetric permutation, use symmetric permutation for symmetric matrices");
57: }
58: ISRestoreIndices(iperm,&riip);
59: ISDestroy(iperm);
61: if (!a->inew){
62: PetscMalloc((mbs+1 + 2*(a->i[mbs]))*sizeof(PetscInt),&ai);
63: aj = ai + mbs+1;
64: } else {
65: ai = a->inew; aj = a->jnew;
66: }
67: PetscMemcpy(ai,a->i,(mbs+1)*sizeof(PetscInt));
68: PetscMemcpy(aj,a->j,(a->i[mbs])*sizeof(PetscInt));
69:
70: /*
71: Phase 1: Find row index r in which to store each nonzero.
72: Initialize count of nonzeros to be stored in each row (nzr).
73: At the end of this phase, a nonzero a(*,*)=a(r(),aj())
74: s.t. a(perm(r),perm(aj)) will fall into upper triangle part.
75: */
77: PetscMalloc(mbs*sizeof(PetscInt),&nzr);
78: PetscMalloc(ai[mbs]*sizeof(PetscInt),&r);
79: for (i=0; i<mbs; i++) nzr[i] = 0;
80: for (i=0; i<ai[mbs]; i++) r[i] = 0;
81:
82: /* for each nonzero element */
83: for (i=0; i<mbs; i++){
84: nz = ai[i+1] - ai[i];
85: j = ai[i];
86: /* printf("nz = %d, j=%d\n",nz,j); */
87: while (nz--){
88: /* --- find row (=r[j]) and column (=aj[j]) in which to store a[j] ...*/
89: k = aj[j]; /* col. index */
90: /* printf("nz = %d, k=%d\n", nz,k); */
91: /* for entry that will be permuted into lower triangle, swap row and col. index */
92: if (rip[k] < rip[i]) aj[j] = i;
93: else k = i;
94:
95: r[j] = k; j++;
96: nzr[k] ++; /* increment count of nonzeros in that row */
97: }
98: }
100: /* Phase 2: Find new ai and permutation to apply to (aj,a).
101: Determine pointers (r) to delimit rows in permuted (aj,a).
102: Note: r is different from r used in phase 1.
103: At the end of this phase, (aj[j],a[j]) will be stored in
104: (aj[r(j)],a[r(j)]).
105: */
106: for (i=0; i<mbs; i++){
107: ai[i+1] = ai[i] + nzr[i];
108: nzr[i] = ai[i+1];
109: }
110:
111: /* determine where each (aj[j], a[j]) is stored in new (aj,a)
112: for each nonzero element (in reverse order) */
113: jmin = ai[0]; jmax = ai[mbs];
114: nz = jmax - jmin;
115: j = jmax-1;
116: while (nz--){
117: i = r[j]; /* row value */
118: if (aj[j] == i) r[j] = ai[i]; /* put diagonal nonzero at beginning of row */
119: else { /* put off-diagonal nonzero in last unused location in row */
120: nzr[i]--; r[j] = nzr[i];
121: }
122: j--;
123: }
124:
125: a->a2anew = aj + ai[mbs];
126: PetscMemcpy(a->a2anew,r,ai[mbs]*sizeof(PetscInt));
127:
128: /* Phase 3: permute (aj,a) to upper triangular form (wrt new ordering) */
129: for (j=jmin; j<jmax; j++){
130: while (r[j] != j){
131: k = r[j]; r[j] = r[k]; r[k] = k;
132: ajk = aj[k]; aj[k] = aj[j]; aj[j] = ajk;
133: /* ak = aa[k]; aa[k] = aa[j]; aa[j] = ak; */
134: }
135: }
136: ierr= ISRestoreIndices(perm,&rip);
138: a->inew = ai;
139: a->jnew = aj;
141: if (a->row) {
142: ISDestroy(a->row);
143: }
144: if (a->icol) {
145: ISDestroy(a->icol);
146: }
147: PetscObjectReference((PetscObject)perm);
148: if (a->row) { ISDestroy(a->row); }
149: a->row = perm;
150: PetscObjectReference((PetscObject)perm);
151: if (a->icol) { ISDestroy(a->icol); }
152: a->icol = perm;
154: PetscFree(nzr);
155: PetscFree(r);
156:
157: return(0);
158: }